I don't take anything and nothing in my diet is different from before this problem onset.
I was experiencing the same problem before I took the 3 weeks off. I thought taking the time off would help by refreshing my chest, but it didn't.
I hit chest once a week. Incline bench(12,10,8),flat bench(12,10,8), Incline D.B(12,10),decline hammer(12,12,10), sometimes I'll do flys. The reps are in parenthesis after the exercise and that is what I did before this problem, now that is just my goal, but I usually end up only being able to meet that goal for the first sets of each exercise.